Blockchain Papers

Seval Capraz, Adnan Özsoy

No abstract is available for this record.

Shuichi Katsumata

Many of the recent advanced lattice-based \(\varSigma \)-/public-coin honest verifier (HVZK) interactive protocols based on the techniques developed by Lyubashevsky (Asiacrypt’09, Eurocrypt’12) can be transformed into a non-interactive zero-knowledge (NIZK) proof in the random oracle model (ROM) using the Fiat-Shamir transform. Unfortunately, although they are known to be secure in the classical ROM, existing proof techniques are incapable of proving them secure in the quantum ROM (QROM). Alternatively, while we could instead rely on the Unruh transform (Eurocrypt’15), the resulting QROM secure NIZK will incur a large overhead compared to the underlying interactive protocol.

Hasan Al-Aswad, Wael Elmedany, Chitra Balakrishna, Nedal Ababneh · 5 authors

Smart cities achieved digital transformation of patients’ health records through the use of new technology in IoT healthcare industry. Such technologies of using IoT and remote patient monitoring systems have become dramatically fundamental to reduce the movement of patients, and hence reducing the risk of spreading Covid-19 infection. The Ministry of Health in the Kingdom of Bahrain strives to achieve digital transformation in the healthcare industry, where the National Health Information System (I-SEHA) was launched to provide higher-quality health services. The system interconnects the public healthcare institutes, allowing access to patient’s data from any location without the hassle of moving the files physically. Digitization of medical data of patients and sharing some of the data with other institutions outside the protected networks may lead to major privacy and integrity concerns. This paper introduces Blockchain-based Zero-Knowledge Proof (BZKP) model, which is an IoT-based patient-centric model that fuses a zero-knowledge proof solution to be developed for protecting patient’s privacy, and ensures patients prior consent on any access to their data including their health status and account balance. The proposed model is developed to provide a robust and scalable architecture for data sharing, which protects the privacy of sensitive data while maintaining high availability. It also provides strong trust and integrity of data by using the immutability features of the blockchain. BZKP is based on pre-approved blockchain access tokens to address challenges of accountability and privacy in Bahrain smart cities. As a result, the model provides a secure and trusted access model between different stakeholders to share patient data while maintaining privacy, trust, and high availability. The zero-knowledge proof can be used with the smart contracts, which provides programmable actions that can be used for automating the prescriptions dispensation process for private pharmacies in a decentralized manner with high confidence. Finally, it recommends enhanced electronic key (eKey) procedures used by eGovernment of the Kingdom of Bahrain to update the smart card which stores the personal keys for protecting patient’s privacy and provide better consent.

Raimu Isuzugawa, Daiki Miyahara, Takaaki Mizuki

No abstract is available for this record.

Kenneth A. Bamberger, Ran Canetti, Shafi Goldwasser, Rebecca Wexler · 5 authors

No abstract is available for this record.

Xavier Salleras, Vanesa Daza

Zero-Knowledge Proofs (ZKPs) are cryptographic primitives allowing a party to prove to another party that the former knows some information while keeping it secret. Such a premise can lead to the development of numerous privacy-preserving protocols in different scenarios, like proving knowledge of some credentials to a server without leaking the identity of the user. Even when the applications of ZKPs were endless, they were not exploited in the wild for a couple of decades due to the fact that computing and verifying proofs was too computationally expensive. However, the advent of efficient schemes (in particular, zk-SNARKs) made this primitive to break into the scene in fields like cryptocurrencies, smart-contracts, and more recently, self-sovereign scenarios: private-by-design identity management and authentication. Nevertheless, its adoption in environments like the Internet of Things (IoT) remains unexplored due to the computational limitations of embedded systems. In this paper, we introduce ZPiE, a C library intended to create ZKP applications to be executed in embedded systems. Its main feature is portability: it can be compiled, executed, and used out-of-the-box in a wide variety of devices. Moreover, our proof-of-concept has been proved to work smoothly in different devices with limited resources, which can execute state-of-the-art ZKP authentication protocols.

Tsz Hon Yuen, Handong Cui, Xiang Xie

No abstract is available for this record.

Daniel Benarroch, Matteo Campanelli, Dario Fiore, Kobi Gurkan · 5 authors

Abstract We consider the problem of proving in zero knowledge that an element of a public set satisfies a given property without disclosing the element, i.e., for some u , “ $$u \in S$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>u</mml:mi><mml:mo>∈</mml:mo><mml:mi>S</mml:mi></mml:mrow></mml:math> and P ( u ) holds”. This problem arises in many applications (anonymous cryptocurrencies, credentials or whitelists) where, for privacy or anonymity reasons, it is crucial to hide certain data while ensuring properties of such data. We design new modular and efficient constructions for this problem through new commit-and-prove zero-knowledge systems for set membership , i.e. schemes proving $$u \in S$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>u</mml:mi><mml:mo>∈</mml:mo><mml:mi>S</mml:mi></mml:mrow></mml:math> for a value u that is in a public commitment $$c_u$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>c</mml:mi><mml:mi>u</mml:mi></mml:msub></mml:math> . We also extend our results to support non-membership proofs , i.e. proving $$u \notin S$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>u</mml:mi><mml:mo>∉</mml:mo><mml:mi>S</mml:mi></mml:mrow></mml:math> . Being commit-and-prove, our solutions can act as plug-and-play modules in statements of the form “ $$u \in S$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>u</mml:mi><mml:mo>∈</mml:mo><mml:mi>S</mml:mi></mml:mrow></mml:math> and P ( u ) holds” by combining our set (non-)membership systems with any other commit-and-prove scheme for P ( u ). Also, they work with Pedersen commitments over prime order groups which makes them compatible with popular systems such as Bulletproofs or Groth16. We implemented our schemes as a software library, and tested experimentally their performance. Compared to previous work that achieves similar properties—the clever techniques combining zkSNARKs and Merkle Trees in Zcash—our solutions offer more flexibility, shorter public parameters and $$3.7 \times $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>3.7</mml:mn><mml:mo>×</mml:mo></mml:mrow></mml:math> – $$30\times $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>30</mml:mn><mml:mo>×</mml:mo></mml:mrow></mml:math> faster proving time for a set of size $$2^{64}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mn>2</mml:mn><mml:mn>64</mml:mn></mml:msup></mml:math> .

Vadim Lyubashevsky, Ngoc Khanh Nguyen, Gregor Seiler

No abstract is available for this record.

Carsten Baum, Alex J. Malozemoff, Marc B. Rosen, Peter Schöll

Zero knowledge proofs are an important building block in many cryptographic applications. Unfortunately, when the proof statements become very large, existing zero-knowledge proof systems easily reach their limits: either the computational overhead, the memory footprint, or the required bandwidth exceed levels that would be tolerable in practice. We present an interactive zero-knowledge proof system for boolean and arithmetic circuits, called $$\mathsf {Mac'n'Cheese}$$ , with a focus on supporting large circuits. Our work follows the commit-and-prove paradigm instantiated using information-theoretic MACs based on vector oblivious linear evaluation to achieve high efficiency. We additionally show how to optimize disjunctions, with a general OR transformation for proving the disjunction of m statements that has communication complexity proportional to the longest statement (plus an additive term logarithmic in m). These disjunctions can further be nested, allowing efficient proofs about complex statements with many levels of disjunctions. We also show how to make $$\mathsf {Mac'n'Cheese}$$ non-interactive (after a preprocessing phase) using the Fiat-Shamir transform, and with only a small degradation in soundness. We have implemented the online phase of $$\mathsf {Mac'n'Cheese}$$ and achieve a runtime of 144 ns per AND gate and 1.5 $$\upmu $$ s per multiplication gate in $$\mathbb {F} _{2^{61} - 1} $$ when run over a network with a 95 ms latency and a bandwidth of 31.5 Mbps. In addition, we show that the disjunction optimization improves communication as expected: when proving a boolean circuit with eight branches and each branch containing roughly 1 billion multiplications, $$\mathsf {Mac'n'Cheese}$$ requires only 75 more bytes to communicate than in the single branch case.

D. O. Kondyrev

The paper analyzes the privacy preserving problem for distributed ledgers. It provides an overview of technologies such as mixers, zero-knowledge proof algorithms, homo- morphic encryption, secure multi-party computation, anonymous signatures, and hardware solutions. Advantages and disadvantages of each technology are identified, as well as usage samples in the existing distributed ledgers. As a result, unsolved problems and prospects for further research are formulated.

Yasminar Amaerita Telaumbanua

Writing skripsi is an obligatory scientific work for students at the last semester at English education study program of IKIP Gunungsitoli. It is done through a research. The research is conducted based on a certain research design. Teacher-researcher did a research to describe what article errors done by the students, how many times the students are writing article errors and why the students cannot revise the article errors successfully particularly in Chapter I. The data source was from the three skripsi done by three students who graduated faster, 3 years and half. As the research findings, the teacher-researcher found there were three kinds of article errors done by the three students in their skripsi in Chapter I namely indefinite article (a, an), definite article (the) and zero article. It’s concluded that the article errors which were done by the three students who wrote their skripsi are indefinite articles (a, an), definite article (the) and zero article, the three students write article errors as 34 times of 27 sentences and the three students cannot revise the article errors successfully because lack of knowledge of using articles as well as lack of attention to find out proof readers to make better papers.

Lihua Song, Xinran Ju, Zongke Zhu, Mengchen Li

Abstract Information security has become the focus problem in the Internet of Things, and the traditional centralized access control model is faced with threats such as single point failure, internal attack, and central leak. In this paper, we proposed a model to improve the access control security of the Internet of Things, which is based on zero-knowledge proof and smart contract technology in the blockchain. Firstly, we deployed the attribute information of access control in the blockchain, which relieves the pressure and credibility problem brought by the third-party information concentration; Secondly, the encrypted access control token is used to gain the access permission of the resources, which makes the user's identity invisible and effectively avoids the attribute ownership exposure problem; Besides, the use of smart contracts solves the problem of low computing efficiency of Internet of Things devices and the waste of blockchain computing power resources; Finally, a prototype of Internet of Things access control system based on blockchain and zero-knowledge proof technology is implemented. The test analysis results show that the model achieves effective attribute privacy protection, compared with the Attribute-Based Access Control model of the same security level, the access efficiency increases linearly with the increase of access scale.

Zhaofeng Ma, Lingyun Wang, Weizhe Zhao

The development of the Internet of Things (IoT) technology has achieved remarkable results in recent years. A large number of sensors and machinery are connected, and combined with the Internet, to achieve intelligent management and operation. However, the traditional centralized IoT data management solution inevitably encounters challenges of data trust, security, sustainability, and user privacy is difficult to guarantee. This paper takes the intelligent transportation sensor network as an example and proposes a blockchain-based Internet of Vehicles (IoV) data secure sharing scheme (called IoVChain), which implements automatic registration, rapid authentication, and reliable sharing method of IoV data through smart contract. The smart contract performs homomorphic encryption and zero-knowledge proof processing on the sensitive part of the data, and this part exists in the form of ciphertext on the blockchain. We adopt PBFT consensus mechanism to ensure the consistency of the entire network ledger, and all the IoV data processing and usage procedure is stored in the Merkle-tree-based block, which cannot be tampered with. Compared with the centralized IoV data management solution, the IoVChain scheme avoids the risk of single point of failure, and keeps the IoV data credible, available, and tamper-resistant under the premise of privacy and security, so that the data can be traced when needed. We have implemented the IoVChain scheme based on the consortium blockchain for trusted and secure sharing of IoV data. Finally, analysis and evaluation show that the proposed IoVChain scheme is feasible, safe, and extensible for the secure sharing of IoV data.

顺东 LI, 文丽 WANG, 润萌 DU

Secure multiparty computation is a focus of the international cryptographic community. The millionaires problem is the most important problem in secure multiparty computation and is a building block for constructing other secure multiparty computation protocols. Several solutions are available to solve this problem, but except for protocols based on garbled circuits, the existing solutions based on public key cryptosystems are only secure in semihonest models. No solution based on a public key cryptosystem is secure against malicious adversaries. This state restricts the resolution of many secure multiparty computation problems in malicious scenarios. A solution that is secure in malicious models is highly applicable in practical application scenarios and is generally appealing. Therefore, the study of the solution to the millionaires problem in a malicious model is of great theoretical and practical significance. In this work, we propose a multiparty computation protocol for the millionaires problem that is secure in a semihonest model. The proposed protocol is simple and easily understandable. We analyze the possible malicious behaviors in this protocol and use zero-knowledge proof and cut-and-choose techniques to resist possible malicious behaviors and thereby convert the protocol into one that is secure in the malicious model. We prove that the proposed protocol is secure in the malicious model by using the well-accepted ideal-real paradigm. Theoretical efficiency analysis shows that the efficiency of our protocol is at least six times that of existing protocols.

Zeba Mahmood, Vacius Jusas

Block-chain emerged as the technology of choice for most applications because of its immutability property. Block-chain's immutability property promotes network resilience against any removal or modification of data stored on the ledger. However, large scale networks such as the Internet of Things (IoT) that may contain millions of nodes can significantly increase Block-chain size and raise serious privacy challenges. Moreover, the General Data Protection Regulations (GDPRs) that were enforced in May 2018 by European countries allows individuals and organizations to take control of their data by establishing stringent rules which includes “the right to be forgotten”. In cases where there are ethical or legal reasons individuals and companies might want their personal data stored to be erased whether such data is stored locally or on the ledger. The philosophy underpinning Block-chains is that forcing nodes to erase data is akin to denying them a role to play in the Block-chain ecosystems as full nodes. In this paper, we attempt to challenge this notion by proposing a model framework for an enhanced privacy that is akin to Block-chain erasure. Our approaches combine ring signatures (that have long been used to generate anonymous signatures) and Zero-Knowledge Proofs (ZKPs) that can help to disguise user's wallet addresses.

Takeshi Miyamae, K. Matsuura

In blockchain-based anonymous cryptocurrencies, due to their tamper-resistance and transparency characteristics, transaction data are initially required to be anonymous, with the help of various cryptographic techniques, e.g., commitment schemes and zero-knowledge proofs. Also, cryptocurrencies are different from existing anonymous messaging protocols regarding the software architecture and the underlying security model. Due to these differences, the sense of anonymity must be specifically defined for anonymous cryptocurrencies, and the anonymity in each anonymous cryptocurrency must be analyzed and evaluated based on the specific architecture model. In this paper, we first propose a specific architecture model with three software layers to anonymous cryptocurrencies. Next, we introduce definitions of fundamental privacy properties (Pfitzmann's anonymity, unlinkability, and pseudonymity) and comprehensively analyze each privacy property for each architecture layer of anonymous cryptocurrencies to establish a privacy evaluation policy for anonymous cryptocurrencies. Finally, we fairly compare the privacy of current leading anonymous cryptocurrencies (e.g., Zerocash, CryptoNote, and Mimblewimble) using the privacy evaluation policy.

Pouriya Alikhani, Nicolas Brunner, Claude Crépeau, Sébastien Designolle · 8 authors

Protecting secrets is a key challenge in our contemporary information-based era. In common situations, however, revealing secrets appears unavoidable, for instance, when identifying oneself in a bank to retrieve money. In turn, this may have highly undesirable consequences in the unlikely, yet not unrealistic, case where the bank's security gets compromised. This naturally raises the question of whether disclosing secrets is fundamentally necessary for identifying oneself, or more generally for proving a statement to be correct. Developments in computer science provide an elegant solution via the concept of zero-knowledge proofs: a prover can convince a verifier of the validity of a certain statement without facilitating the elaboration of a proof at all. In this work, we report the experimental realisation of such a zero-knowledge protocol involving two separated verifier-prover pairs. Security is enforced via the physical principle of special relativity, and no computational assumption (such as the existence of one-way functions) is required. Our implementation exclusively relies on off-the-shelf equipment and works at both short (60 m) and long distances ($\geqslant$400 m) in about one second. This demonstrates the practical potential of multi-prover zero-knowledge protocols, promising for identification tasks and blockchain applications such as cryptocurrencies or smart contracts.

Jeffrey A. Young, Amar Rasheed, Ray R. Heshemi, Ayman Bagabas

The Internet of Things (IoT) is completely transforming the way network-connected devices are made. Manufacturers and intelligent transportation systems are using thousands of IoT devices and machine-to-machine communication to drive industrial automation. Existing access control schemes for IoT authentication fail to support user anonymity. They rely on the surrendering of the device/user authentication parameters to the trusted server, which hence can be utilized by the IoT infrastructure to track users' behavioral patterns. Furthermore, existing access control mechanisms lack the support of run-time integrity assessment capabilities that are used to verify the authenticity of an authentication process during execution. This paper presents a parametrized crypto-based privacy-preserving authentication protocol that support anonymity, it is based on Zero Knowledge Proof (ZKP). Without the loss of anonymity, a methodological framework for bootstrapping a parametrized authentication process's integrity is introduced herein. We show that run-time integrity assessment of an authentication process running on an IoT device can be achieved through the utilization of the IoT device's physical characteristics, specifically energy consumption and computation time. Behavioral patterns based on the device's power/energy consumption for the ZKP-based protocol were captured and recorded during this effort. In addition, fine-grained behavioral patterns that capture the authentication protocol's processing time were collected and analyzed. To validate the proposed scheme, it was fully implemented and deployed on an IoT testbed. We have tested the performance of the proposed scheme in terms of power consumption and computation time.

Kaida Jiang, Yifei Gao, Jiawei Xiao, Futai Zou

In traditional centralized application construction and data storage modes, the application servers and the users are not in equal position in user information management. The application server can store and abuse the user's information under the circumstances that the users are not aware, and the user cannot revoke the authorization from the application server. Therefore, this paper proposes an identity management system combined with blockchain technology, which can return the management right of user information to users. This system adopts a three-layer architecture composed of blockchain layer, virtual chain layer and storage layer, and encapsulates all functions in each layer. It has good flexibility, and is easy to add new technologies, with good extensibility. The blockchain records the user's information state to realize the consensus and integrity of the user's data. The virtual chain layer is responsible for the main logical functions and encapsulates the user's request into a blockchain transaction, maintaining a good portability. The storage layer is responsible for the actual file storage and is responsible for file routing, backup, and query. Comprehensively speaking, based on the above three layers' architecture, the system implements the user's privacy granularity control, the user file's external storage, and combines the zero-knowledge proof to update the user's private key. In view of the application environment of this system, the access time delay and efficiency of the P2P storage system are simulated. It solves the problems of centralized application construction and data storage mode under which users cannot fully control personal information and privacy protection.

Sabater, César, Bellet, Aurélien, Ramon, Jan

Learning from data owned by several parties, as in federated learning, raises challenges regarding the privacy guarantees provided to participants and the correctness of the computation in the presence of malicious parties. We tackle these challenges in the context of distributed averaging, an essential building block of distributed and federated learning. Our first contribution is a novel distributed differentially private protocol which naturally scales with the number of parties. The key idea underlying our protocol is to exchange correlated Gaussian noise along the edges of a network graph, complemented by independent noise added by each party. We analyze the differential privacy guarantees of our protocol and the impact of the graph topology, showing that we can match the accuracy of the trusted curator model even when each party communicates with only a logarithmic number of other parties chosen at random. This is in contrast with protocols in the local model of privacy (with lower accuracy) or based on secure aggregation (where all pairs of users need to exchange messages). Our second contribution is to enable users to prove the correctness of their computations without compromising the efficiency and privacy guarantees of the protocol. Our construction relies on standard cryptographic primitives like commitment schemes and zero knowledge proofs.

Oluwatobiloba Ololade

The quick jumps in developing new digital identity technologies have resulted in this trend of developing privacy-preserving solutions in Know Your Customer (KYC) verification systems. This article delves into the evolution of an Advanced Digital Identity Orchestration Engine to enhance privacy protection in the KYC processes. With the rise of concerns surrounding data privacy and security, traditional knowledge of customer systems which are based on centralized database, have faced major challenges including data breaches and unauthorized access. In contrast, the proposed identity orchestration engine draws on the use of Self-Sovereign Identity (SSI) principles, blockchain technology, and verifiable credentials to offer a decentralized, secure and privacy-preserving solution to identity management problem. This engine allows users to manage their personal identity information, and selectively share their information with entities they trust without losing their privacy. By leveraging decentralized identifiers (DIDs) and public key cryptography, the system is enabled to ensure the sensitive data isn't kept in a central place causing reduction in the odds of unauthorized access. Furthermore, features such as zero knowledge proofs (ZKPs) and selective disclosure provide the option for a granular control on what data is shared to ensure that only the required information is provided to comply with regulation requirements. This article also talks about integrating the orchestration engine with existing frameworks for KYC and explores the scalability, interoperability, and potential for this engine to help increase inclusivity in digital identity management. Through case studies and real-world examples, the paper points out the efficiency in working of this engine in getting better security and privacy and user experience in the process of KYC verification. Ultimately, the solution proposed creates a major step forward to privacy-preserving and user-centric digital Identity systems adapted both globally to regulatory requirements and to increase trust in digital financial services.

Aman Luthra, James Cavanaugh, Hugo Renzzo Olcese, Rina M. Hirsch · 5 authors

Consider the problem of auditing an investment fund. This usually involves inspecting each transaction in its trading history, and accumulating its capital gains and losses, so that its net asset value can be computed precisely to avoid financial frauds. We present ZeroAUDIT, a confidential and privacy preserving auditing platform, which accomplishes this goal without having to know any of a transaction’s details. Sitting at the heart of the system is a zero knowledge proof protocol, in the discrete logarithm setting, which allows one to reason about the elements of a Merkle tree. Using it, we can prove that a trading transaction is occurring at a fair market price without disclosing which securities are being traded. We have implemented the system on the Hyperledger Fabric platform and we report the use of batch verification techniques in improving its efficiency.

Prabhanjan Ananth, Kai-Min Chung, Rolando L. La Placa

We study the notion of zero-knowledge secure against quantum polynomial-time verifiers (referred to as quantum zero-knowledge) in the concurrent composition setting. Despite being extensively studied in the classical setting, concurrent composition in the quantum setting has hardly been studied. We initiate a formal study of concurrent quantum zero-knowledge. Our results are as follows: -Bounded Concurrent QZK for NP and QMA: Assuming post-quantum one-way functions, there exists a quantum zero-knowledge proof system for NP in the bounded concurrent setting. In this setting, we fix a priori the number of verifiers that can simultaneously interact with the prover. Under the same assumption, we also show that there exists a quantum zero-knowledge proof system for QMA in the bounded concurrency setting. -Quantum Proofs of Knowledge: Assuming quantum hardness of learning with errors (QLWE), there exists a bounded concurrent zero-knowledge proof system for NP satisfying quantum proof of knowledge property. Our extraction mechanism simultaneously allows for extraction probability to be negligibly close to acceptance probability (extractability) and also ensures that the prover's state after extraction is statistically close to the prover's state after interacting with the verifier (simulatability). The seminal work of [Unruh EUROCRYPT'12], and all its followups, satisfied a weaker version of extractability property and moreover, did not achieve simulatability. Our result yields a proof of quantum knowledge system for QMA with better parameters than prior works.